People take part in flash mobs for entertainment, fun and testing new unusual feelings. People also want to forget their usual life and hang out with big crowd. In September 2009, in New York, in Brooklyn thousands of citizens appear in streets with their invisible pets. New York art group Improve Everywhere organized a flash mob, during which anyone could walk around the city with their loved but non-existent dog. The participants tried to create the effect of the presence of pets in different ways. They made special collars on a strong base and behave in different ways. People touched their pets, were wandering through streets and also going into cafes with them. Waiters brought them special bowls with food. It’s was so unusual and interesting event and I want to take part in it.